Ouch! Just wanted to share my experience, not mastitis but an infection all the same
I had an infection, which turned out to be topical so cleared with very strong antibiotics, both via the drip and oral - had a 5 day stint in hospital to manage same as it was every 4 hours. I was told that infections can take a lot to shift - so perhaps you are in need of further antibiotics. Do you have a breast care nurse? When my infection started I couldn't get to see my GP so I rang my Breast care nurse and she got onto the Breast Surgeon and the visit and treatment started immediately. He rang me and asked for a photo to be sent on the mobile phone and then rang again and said pack your bag you're coming in here and Angela my darling Breast care nurse greeted me and the treatment started. It was weeks of oral antibiotics, had to set the alarm as I needed to be disciplined as we wanted it shifted before my next surgery. We got on top of it. When they opened me up again for changeover surgery (11 weeks later) there was no sign of infection and we were all pleased as it was then confirmed that it was only topical.
Hope it clears soon for you, take care